Abstract:
The impact of a typical pre-monsoon season
(April–June) dust storm event on the regional aerosol opti-
cal properties and radiation budget in northern India is an-
alyzed. The dust storm event lasted from 17 to 22 April
2010 and the Weather Research and Forecasting model
coupled with Chemistry (WRF-Chem) estimated total dust
emissions of 7.5 Tg over the model domain. Both in situ
(AERONET – Aerosol Robotic Network) and satellite obser-
vations show significant increase (> 50 %) in local to regional
scale aerosol optical depth (AOD) and decrease (> 70 %)
in the Ångström exponent (α) during this period. Amongst
the AERONET sites in this region, Kanpur was influenced
the most, where the AOD reached up to 2.1 and the α de-
creased to −0.09 during the dust storm period. The WRF-
Chem model reproduced the spatial and temporal distribu-
tions of dust plumes and aerosol optical properties but gen-
erally underestimated the AOD. The average MODIS and
WRF-Chem AOD (550 nm) values in a subregion (70–80◦ E,
25–30◦ N) affected the most by the dust storm are estimated
as 0.80 ± 0.30 and 0.68 ± 0.28, respectively. Model results
show that dust particles cool the surface and the top of the at-
mosphere, but warm the atmosphere itself. The radiative per-
turbation due to dust aerosols averaged over the subregion is
estimated as −2.9 ± 3.1 W m⁻² at the top of the atmosphere,
5.1 ± 3.3 W m⁻² in the atmosphere and −8.0 ± 3.3 W m⁻²
at the surface. The simulated instantaneous cooling under
the dust plume was much higher and reached −227 and
−70 W m⁻² at the surface and the top of the atmosphere, re-
spectively. The impact of these radiative perturbations on the
surface energy budget is estimated to be small on a regional
scale but significant locally.
